This project tests specific hypotheses about dependencies between language comprehension and production, which are typically studied independently. The PI's production-distribution-comprehension (PDC) account holds that utterance planning choices during language production yield distributional patterns in the language, in which certain syntactic structures co-vary with particular word choices, messages, and discourse environments. Comprehenders, through statistical learning during prior comprehension experiences, become highly sensitive to these patterns, and this sensitivity guides comprehension processes. Thus, many aspects of comprehension can ultimately be traced to task demands related to language production. Specific aims of the project include: (1) Link syntactic structure choice in production to mechanisms of sentence planning. (2) Compare the PDC account of comprehension to alternative views of relative clause interpretation. (3) Test the causal relations between production constraints, distributional patterns in the language, and comprehension performance. (4) Relate adult sentence comprehension to statistical learning. (5) Test the current limits of constraint-based models of language comprehension. The PDC approach offers a significant alternative to other views and also may inform language acquisition research by illuminating the role of distributional patterns in child language acquisition. The work also can inform language therapies for brain injured patients in several ways. First, sources of production difficulty are precisely investigated, as are accommodations that unimpaired speakers make in the face of this difficulty. Second, the project investigates the relationship between prior experience with a syntactic construction and comprehension difficulty, which can have implications for the amount and nature of practice that should be provided to patients to improve their comprehension of certain sentence types.